1. Technical Field
The present invention relates to a semiconductor device and a method for manufacturing the same.
2. Related Art
Recent years have seen rapid advances in reducing the size and power consumption of semiconductor devices. With increased variation in the kinds of transistors accompanying these advances, high breakdown voltage transistors and low breakdown voltage transistors have come to be formed on the same semiconductor substrate.
FIGS. 8 to 10 in JP-A-2006-135102 show that an oxide film is formed at the same time as the formation of an element-isolating insulation film of a low breakdown voltage transistor, and the oxide film is used as an electric field-relaxing insulation film below the gate electrode of a high breakdown voltage transistor.
Also, in addition to this, FIGS. 2 to 5 in JP-A-2006-135102 show that the element-isolating insulation film of the low breakdown voltage transistor and the electric field-relaxing insulation film below the gate electrode of the high breakdown voltage transistor are formed in separate steps.
However, with the technique shown in FIGS. 8 to 10 in JP-A-2006-135102, the thickness of the element-isolating insulation film of the low breakdown voltage transistor and the thickness of the electric field-relaxing insulation film of the high breakdown voltage transistor are approximately the same. For this reason, there are cases where it is not possible to meet the requirement of reducing the on-resistance by reducing the thickness of the electric field-relaxing insulation film of the high breakdown voltage transistor.
Also, with the technique shown in FIGS. 2 to 5 in JP-A-2006-135102, the exposure alignment for forming the element-isolating insulation film of the low breakdown voltage transistor and the exposure alignment for forming the electric field-relaxing insulation film of the high breakdown voltage transistor need to be performed separately. For this reason, it is necessary to take up more of the alignment margin and there are cases where it is not possible to meet the requirement of reducing the size.
An advantage of some aspects of the invention is to reduce the on-resistance of a high breakdown voltage transistor that has an electric field-relaxing insulation film and to enable a reduction in size.